Recently, there is dramatically growing demand for portable electronic products such as laptop computers, video cameras and mobile phones, and with the extensive development of electric vehicles, accumulators for energy storage, robots and satellites, many studies are being made on high performance secondary batteries that can be recharged repeatedly.
Currently, commercially available secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium secondary batteries and the like, and among them, lithium secondary batteries have little or no memory effect, and thus they are gaining more attention than nickel-based secondary batteries for their advantages of free charging and discharging, very low self-discharging and high energy density.
A battery pack applied to electric vehicles generally includes a plurality of battery modules connected in series and a plurality of battery management systems (BMSs). Each BMS monitors and controls the state of the battery module that the BMU manages. Recently, to meet the demand for high-capacity high-output battery packs, the number of battery modules included in a battery pack also increases. To efficiently manage the state of each battery module included in the battery pack, a single master-multi slave structure is disclosed. The single master-multi slave structure includes a plurality of slave BMSs installed in each battery module and a master BMS that controls the overall operation of the plurality of slave BMSs. In this instance, communication between the plurality of slave BMSs and the master BMS may be performed by a wireless method.
Each of the plurality of slave BMSs transmits a wireless signal to the master BMS or receives a wireless signal from the master BMS using electrical energy of the battery module in which the slave BMS is coupled.
Meanwhile, due to the environment in which the battery pack operates or the electrical and chemical properties of the individual battery module, a residual capacity deviation often occurs between the plurality of battery modules. To reduce the residual capacity deviation between the plurality of battery modules, balancing control is necessary.
However, most of conventional technologies related to balancing have applications in systems designed for communication between a plurality of slave BMSs and a master BMS through wired means such as a cable.